JP2014092400A - Measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an accurate noise figure of a measured object without considering an influence of residual spurious during implementation of measurement processing.SOLUTION: The measurement device comprises: a measurement management part 11 that, when implementation of calibration processing is instructed to an input operation part, calibrates the measurement device, using a noise figure of the measurement device measured with a measurement frequency as a calibration value and, when the implementation of the measurement processing is instructed to the input operation part, measures the noise figure of the measured object with the measurement frequency; a residual spurious judgement part 14 that, when the measurement management part implements the calibration processing, judges whether or not the noise figure in the measurement frequency is affected by the influence of the residual spurious; and a measurement frequency shift part 15 that, when the residual spurious judgement part judges that the noise figure in the measurement frequency is affected by the influence of the residual spurious, shifts the measurement frequency such that a frequency having the measurement frequency added or reduced by a prescribed frequency is a measurement frequency.

Description

  The present invention relates to a measuring apparatus that measures a noise figure of an object to be measured by a Y factor method.

  Noise figure (Noise Figure) is one of important parameters used in evaluating the performance of a radio or transceiver for processing weak signals under thermal noise. Such a noise figure is measured by, for example, a Y factor method using a spectrum analyzer.

  The Y factor method uses a Y factor which is a ratio of input power to output power obtained when a noise source of a known size is connected to a device under test and the noise source is turned on and off. This is a method for measuring the noise figure of the device under test.

A conventional measurement method using such a Y-factor method is a step of adding a measurement signal TEST as an input to the DUT, where the measurement signal TEST is simultaneously in the first frequency band with the first power P _H and the second power. Having a second power P _C in the frequency band of the DUT, causing the DUT to generate the output signal OUTPUT in response to the measurement signal TEST, and the output signal OUTPUT has a third power P _HO in the first frequency band. Measuring the third power P _HO and the fourth power P _CO of the output signal OUTPUT, the one having the fourth power P _CO in the second frequency band, and the noise factor as the first power factor measuring method and a step of calculating as a combination of respective values of the power P _H and the second power P _C and the third power P _HO and fourth power P _CO is known (e.g., Patent Document 1 reference).

JP-T-2002-528724

  However, since the conventional measuring apparatus does not consider the residual spurious of the measuring apparatus itself and is not supposed to cope with it, the measuring apparatus itself is executed when performing the measurement process for measuring the noise figure of the object to be measured. There is a problem that the noise figure of the object to be measured may not be accurately measured due to the presence of residual spurious.

  The present invention has been made to solve the conventional problems, and is capable of measuring an accurate noise figure of an object to be measured without performing the effect of residual spurious when performing measurement processing. An object of the present invention is to provide a measuring apparatus capable of performing the above.

  The measurement apparatus of the present invention includes a measurement process for measuring the noise figure of the object to be measured (20) by a Y factor method using a noise source having a known excess noise ratio, and a known excess before the measurement process is executed. A measurement apparatus (10) for executing a calibration process for obtaining a calibration value by a Y-factor method using a noise source having a noise ratio, the execution instruction for any of the measurement process and the calibration process, and the noise figure And an input operation unit (17) to which a measurement frequency for measuring is input, and when the input operation unit is instructed to execute the calibration process, the noise figure of the measurement device is measured at the measurement frequency. The measurement device is calibrated using the measured noise figure as a calibration value, and when the input operation unit is instructed to execute the measurement process, the measurement frequency is set to And a measurement management unit (11) for measuring the noise figure of the device under test, and the noise figure at the measurement frequency has an effect of residual spurious when the measurement management unit is executing the calibration process. A residual spurious determination unit (14) that determines whether or not the signal is received, and the residual spurious determination unit determines that the noise figure at the measurement frequency input by the input operation unit is affected by the residual spurious. A measurement frequency shift unit (15) that shifts the measurement frequency so that a frequency obtained by increasing or decreasing the measurement frequency by a predetermined frequency becomes the measurement frequency. ing.

  With this configuration, when the measurement apparatus of the present invention determines that the noise figure at the measurement frequency is affected by the residual spurious during the calibration process, the measurement apparatus increases or decreases the measurement frequency by a predetermined frequency. Because the measured frequency is shifted so that the measured frequency becomes the measured frequency, it is possible to measure the accurate noise figure of the object under measurement without considering the effect of residual spurious when performing the measurement process. it can.

  In the measurement apparatus of the present invention, the predetermined frequency may correspond to the resolution of the measurement apparatus.

  With this configuration, the measurement device of the present invention can measure an accurate noise figure without degrading the measurement accuracy of the measurement device because the predetermined frequency corresponds to the resolution of the measurement device.

  In the measurement apparatus of the present invention, the residual spurious determination unit compares the noise figure at the measurement frequency of the measurement apparatus measured by the measurement management unit with a predetermined threshold, so that the noise figure at the measurement frequency affects the influence of the residual spurious. You may make it judge whether it has received.

  With this configuration, the measurement apparatus of the present invention can measure a predetermined accurate noise figure because the noise figure at the measurement frequency is compared with a predetermined threshold.

  The measurement method using the measurement apparatus of the present invention includes a measurement process for measuring the noise figure of the object to be measured (20) by a Y factor method using a noise source having a known excess noise ratio, A measurement method using a measurement apparatus (10) that executes a calibration process for obtaining a calibration value by a Y-factor method using a noise source having a known excess noise ratio before execution, the measurement process and the measurement process An input step in which an execution instruction for any calibration process and a measurement frequency for measuring the noise figure are input, and when the execution of the calibration process is instructed in the input step, the measurement apparatus at the measurement frequency The noise figure of the measurement apparatus is measured, the measurement apparatus is calibrated using the measured noise figure of the measurement apparatus as a calibration value, and the measurement is performed in the input step. A measurement step for measuring the noise figure of the object to be measured at the measurement frequency, and the noise at the measurement frequency when the calibration process is being executed in the measurement step. In the residual spurious determination step for determining whether or not the exponent is affected by the residual spurious, and in the residual spurious determination step, the noise factor at the measurement frequency input in the input step is affected by the residual spurious. A measurement frequency shift step of shifting the measurement frequency so that a frequency obtained by increasing or decreasing the measurement frequency by a predetermined frequency becomes the measurement frequency.

  With this configuration, in the measurement method using the measurement apparatus of the present invention, when performing the calibration process, if it is determined that the noise figure at the measurement frequency is affected by the residual spurious, the measurement frequency is set to a predetermined frequency. Since the measurement frequency is shifted so that the frequency increased or decreased is the measurement frequency, the accurate noise figure of the object to be measured can be calculated while performing the measurement process without considering the effect of residual spurious. Can be measured.

  In the measurement method using the measurement apparatus of the present invention, a predetermined frequency may correspond to the resolution of the measurement apparatus.

  With this configuration, the measurement method using the measurement apparatus of the present invention measures an accurate noise figure without degrading the measurement accuracy of the measurement apparatus because a predetermined frequency corresponds to the resolution of the measurement apparatus.

  In the measurement method using the measurement device of the present invention, in the residual spurious determination step, the noise figure at the measurement frequency of the measurement device measured at the measurement step is compared with a predetermined threshold value, so that It may be determined whether the noise figure is affected by residual spurious.

  With this configuration, the measurement method using the measurement apparatus of the present invention compares the noise figure at the measurement frequency with a predetermined threshold value, so that a predetermined accurate noise figure can be measured.

  According to the present invention, it is possible to provide a measuring apparatus capable of measuring an accurate noise figure of an object to be measured without considering the effect of residual spurious when performing a measurement process.

It is a block diagram of the measuring apparatus which concerns on one embodiment of this invention. It is a figure which shows an example of the measurement frequency designated by the input operation part of the measuring apparatus shown in FIG. It is a figure which shows an example of the list | wrist of the frequency range and threshold value which are stored in the measuring apparatus shown in FIG. 1, (a) is an example of a list, (b) makes it a graph. It is a flowchart which shows an example of operation | movement of the calibration process of the measuring apparatus shown in FIG. FIG. 5 is a diagram illustrating an example of a list indicating measurement results when the calibration process of the measurement apparatus illustrated in FIG. 1 is performed according to the flowchart illustrated in FIG. 4, where (a) is the first measurement result and (b) is The measurement results and the threshold values of the list are graphed. It is a figure which shows an example of the list | wrist which shows the measurement result at the time of performing the calibration process of the measuring apparatus shown in FIG. 1 along the flowchart shown in FIG. 4, (a) shows the measurement result which re-measured the specific measurement frequency. (B) is a graph of the remeasurement results and the list threshold values. It is a conceptual diagram for demonstrating the relationship between a residual spurious at the time of performing the calibration process of the measuring apparatus shown in FIG. 1, and resolution bandwidth (RBW). FIG. 7A shows a case where residual spurious exists in the resolution bandwidth, and FIG. 7B shifts the measurement frequency to a position increased from the measurement frequency by a frequency corresponding to one resolution bandwidth. Shows the case. It is a block diagram for demonstrating the structure at the time of performing the measurement process of the noise figure of a to-be-measured object using the measuring apparatus of one embodiment of this invention shown in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a block configuration of a measuring apparatus 10 according to an embodiment of the present invention. The measurement apparatus 10 includes, for example, measurement of a harmonic level of a signal in a device under test, measurement of device distortion, measurement of a transmission wave of a transmitter, measurement of channel power of a modulation wave, measurement of a modulation frequency and a modulation degree, For example, a spectrum analyzer is applicable, which can analyze a failure related to modulation and measure a harmonic level of a signal.

  The measuring apparatus 10 can execute both a measurement process for measuring the noise figure of the object to be measured and its own calibration process. The measurement apparatus 10 functions as a control unit that controls the entire process of the measuring apparatus 10. A management unit 11 is provided.

  The measurement management unit 11 includes a residual spurious determination unit 14, a measurement frequency shift unit 15, and a storage unit 19. In addition, a parameter management unit 16, an input operation unit 17, a display unit 18, and an N / S controller (noise source controller) 12 are connected to the measurement management unit 11. An instruction to execute the measurement process or the calibration process can be input from the input operation unit 17.

  An outline of the operation of the measurement management unit 11 will be described. When an instruction to execute calibration processing is input from the input operation unit 17, the measurement management unit 11 measures the noise figure of the measurement apparatus 10 itself, and the measurement result Is stored in the storage unit 19.

  Thereafter, when an instruction to execute measurement processing is input from the input operation unit 17, the measurement management unit 11 measures the noise figure of the device under test and stores the measurement result in the storage unit 19. During the measurement process, the measurement management unit 11 corrects the result of the execution of the measurement process using the result of the execution of the calibration process stored in the storage unit 19 to obtain the noise figure of only the object to be measured. .

  As will be described in detail later, when the measurement management unit 11 executes calibration processing and measures the noise figure of the measuring apparatus 10 itself, the residual spurious determination unit 14 determines the residual spurious at the measurement frequency based on the measurement result. It is determined whether or not exists.

  The residual spurious is a frequency component mainly composed of harmonics and included in the AC signal, and is caused by the system design. If the measurement of the noise figure of the object to be measured is performed in a state where the residual spurious exists at the measurement frequency, the measuring device cannot accurately measure the noise figure of the object to be measured due to the presence of the residual spurious.

  For this reason, the measurement frequency shift unit 15 increases the specific measurement frequency by a predetermined frequency when the residual spurious determination unit 14 determines that the residual spurious exists at the specific measurement frequency. The increased frequency becomes a new measurement frequency.

  In this specification, increasing the measurement frequency by a predetermined frequency by the measurement frequency shift unit 15 is referred to as shifting the measurement frequency. Further, the measurement frequency is shifted not only by an increase by a predetermined frequency but also by a decrease.

  The parameter management unit 16 stores a table indicating a list of measurement frequencies of measurement points for noise figure measurement by performing measurement processing and calibration processing.

  The measurement frequency and the number of points at the measurement point are determined by the user of the measurement apparatus 10 in consideration of the purpose of measurement of the noise figure of the device under test 10 and the accuracy required, and input by the input operation unit 17 to manage parameters. Stored in the table of the unit 16.

  An example of a table of a list of measurement frequencies of measurement points stored in the parameter management unit 16 is shown in FIG. The table shown in FIG. 2 indicates that when measuring 4 points, the measurement frequencies of the measurement points are 1 GHz, 2 GHz, 3 GHz, and 4 GHz.

  Further, the parameter management unit 16 has a table in which the display average noise level in a predetermined frequency band to which the measurement frequency belongs is collected as a threshold. The threshold value is changed due to a difference in measurement resolution of the measurement apparatus 10 or the like.

  The threshold value is input by the user of the measuring apparatus 10 through the input operation unit 17 and stored in the table of the parameter management unit 16. The threshold value may be generated by the measurement management unit 11 based on data indicating the main body configuration of the measurement apparatus 10 and stored in the table of the parameter management unit 16.

  The display unit 18 includes, for example, a display screen (not shown) that represents the signal intensity on the vertical axis and the frequency on the horizontal axis, and can display the result measured by the measurement management unit 11. For example, the display unit 18 can continuously display the signal intensity related to the measurement result on the display screen by sweeping from the lowest measurable frequency at the left end of the screen to the highest frequency at the right end of the screen.

  When the measurement process is executed by the Y factor method, the noise figure of the device under test is measured with the device under test and N / S (noise source) 22 connected in series. In FIG. 1, the nodes 20a and 20b are short-circuited, but when the measurement process is executed, the device under test is inserted between the nodes 20a and 20b.

  N / S22 has a guaranteed ENR (excess noise ratio), and for example, one selected from 5 dB to 20 dB is used.

  In other words, N / S22 guarantees a relative noise level between when the noise source is turned on and when it is turned off when the measurement process and the calibration process are executed by the Y factor method. There is no guarantee of absolute values for the upper and lower limits.

  The N / S controller 12 is connected to the N / S 22. The N / S controller 12 controls on / off switching of the N / S 22. When the N / S controller 12 turns on the N / S 22, a signal with a predetermined noise level that is an excess noise ratio is supplied from the N / S 22 to the measurement management unit 11, and when the N / S 22 is turned off, the excess noise A signal having a noise level not including the ratio is supplied to the measurement management unit 11.

  FIG. 1 shows a state in which the N / S 22 is connected to the measurement management unit 11, but the N / S 22 may be connected to the measurement management unit 11 instead of being always connected. Further, in the case of executing another measurement method instead of the Y factor method, N / S 22 can be removed from the measurement management unit 11 according to the measurement method.

  In this embodiment, for example, as shown in FIG. 3A, the measurement management unit 11 is in a band of 2 GHz or more and less than 3 GHz when the measurement frequency is in a band of 1 GHz or more and less than 2 GHz. In the case, when the frequency is 3 GHz or more and less than 4 GHz and when the frequency is 4 GHz or more and less than 5 GHz, −140 dBm, −130 dBm, −160 dBm, and −155 dBm are generated as thresholds, respectively. These are input to the table of the parameter management unit 16 by the input operation unit 17.

  FIG. 3B shows the values shown in the table of FIG. 3A as a graph. In the graph, a short horizontal line represents each frequency band and a threshold within the band, and a black circle at the end of the horizontal line includes the frequency at the end, and a white circle does not include the frequency. Means that.

  For example, when the measurement frequency is in a band lower than that not including 2 GHz but including a value higher than 1 GHz, a short horizontal line representing it indicates a threshold of −140 dBm. As is clear from the graph of FIG. 3B, the threshold value is not continuous and varies depending on the frequency band.

  The thresholds in the list are predetermined based on the results of confirming that residual spurious exists when the thresholds are exceeded by experimenting with each measurement target device. The threshold in the measurement frequency band may be different for each device.

  The parameter management unit 16 stores a predetermined resolution bandwidth (RBW) value. The resolution bandwidth indicates a unit range of the frequency at which the noise level of the measurement apparatus 10 is measured. When the width is narrowed, the measurement accuracy can be improved, but the measurement time becomes long because the probability that the measurement signal hits within the band becomes small.

  On the other hand, if the resolution bandwidth is widened, the measurement time is shortened, but the measurement accuracy is lowered. For this reason, the value is determined and stored in advance by these trade-offs.

  As will be described in detail later, the resolution bandwidth is measured by increasing the measurement frequency by the resolution bandwidth when the measurement frequency shift unit 15 finds that residual spurious exists at the measurement frequency at a specific measurement point. Shift points. The measuring apparatus 10 measures the noise level again at the shifted point.

  The number of measurement frequency shifts corresponding to the resolution bandwidth is about 1 to 2. Thereby, residual spurious can be avoided, and it is not necessary to consider the influence of residual spurious due to the system design of the product when measuring the noise figure of the device under test.

  In this embodiment, the resolution bandwidth is set to 4 MHz, but is not limited to this.

  Based on FIG. 4, the operation when the measurement apparatus 10 executes the calibration process will be described. At that time, reference is made to FIG. 5 and FIG. 6 showing a list and graph of measurement results obtained when the calibration process is executed.

  Before the operation shown in FIG. 4 starts, first, the user of the measuring apparatus 10 directly connects the N / S 22 to the measurement management unit 11 as shown in FIG. Enter the measured frequency.

  The value of the measurement frequency is stored in the table of the parameter management unit 16 by the user of the measurement apparatus 10. In the present embodiment, as shown in FIG. 2, the table stores 1 GHz, 2 GHz, 3 GHz, and 4 GHz as measurement frequencies.

  Next, when the measurement of the calibration process is started, the measurement management unit 11 sets the measurement frequency stored in the table of the parameter management unit 14 to the parameter F (step S41).

  Subsequently, the measurement management unit 11 reads 1 GHz in the measurement frequency from the table of the parameter management unit 16 as the measurement frequency F (step S42).

  When the measurement frequency F is read, the measurement management unit 11 measures the noise level of the measurement apparatus 10 at 1 GHz of the measurement frequency F read from the measurement frequency table (step S43).

  The measurement is performed in a predetermined resolution bandwidth stored in the parameter management unit 16. At this time, the N / S controller 12 supplies the input signal including the predetermined noise signal and the input signal not including the predetermined noise signal to the measurement management unit 11 while switching the N / S 22 on / off. The measurement management unit 11 obtains measurement values in each case.

  When the measurement is completed, the measurement management unit 11 obtains the Y factor from the measurement value when N / S 22 is on and off, and obtains the noise figure of the measurement apparatus 10 at the measurement frequency of 1 GHz from a predetermined formula. The obtained noise figure is stored in the storage unit 19 of the measurement management unit 11 as a measurement result.

  In this embodiment, the noise figure at the measurement frequency of 1 GHz is −150 dBm as shown in FIG. The noise figure is indicated by “x” at the point of the measurement frequency of 1 GHz in FIG.

  Next, the residual spurious determination unit 14 compares the measurement result with a threshold value (step S44).

  Specifically, the residual spurious determination unit 14 reads out −150 dBm of the measurement result from the storage unit of the measurement management unit 11, and from the table of frequency ranges and threshold values stored in the parameter management unit 14, The threshold value in the band to which the measurement frequency at the time of measurement belongs is read. Here, since the measurement frequency is 1 GHz, the threshold value −140 dBm shown in FIG.

  Next, the residual spurious determination unit 14 compares the read threshold value −140 dBm with the measurement result −150 dBm (step S <b> 44).

  In the comparison, the residual spurious determination unit 14 determines that the measurement result −150 dBm is smaller than the threshold −140 dBm. This is apparent from the fact that the measurement result of −150 dBm indicated by “x” is located below the threshold value of −140 dBm at the measurement frequency of 1 GHz as shown in FIG.

  Thus, when the measurement result is smaller than the threshold value, the measurement management unit 11 stores the measurement frequency at which the measurement is performed in the parameter management unit 16 (step S45). In this case, the measurement management unit 11 overwrites the list of the table of the parameter management unit 16 that has read the measurement frequency at the time of measurement. However, the measurement management unit 11 may provide a separate table in the parameter management unit 16 and store the measured frequency after calibration.

  Next, the measurement management unit 11 determines whether there is a next measurement frequency (step S46). Here, since 2 GHz is present as the next parameter in the measurement frequency table of the parameter management unit 16, the measurement management unit 11 continues the measurement. That is, in the flowchart of FIG. 4, the operation returns to step S42.

  Next, the measurement management unit 11 reads out the next parameter of the measurement frequency shown in the list shown in FIG. 2, that is, 2 GHz, as the measurement frequency F from the table stored in the parameter management unit 16 (step S42). ).

  Next, the measurement management unit 11 measures the noise level at 2 GHz read from the measurement frequency table (step S43). At this time, the N / S controller 12 supplies the input signal including the predetermined noise signal or the input signal not including the predetermined noise signal to the measurement management unit 11 while switching the N / S 22 on / off, and performs measurement. The management unit 11 obtains measurement values in each case. Further, these measurements are performed in a predetermined resolution bandwidth stored in the parameter management unit 16.

  When the measurement is completed, the measurement management unit 11 obtains the Y factor from the measurement values when N / S 22 is on and off, and obtains the noise figure of the measurement apparatus 10 at the measurement frequency of 2 GHz from a predetermined formula. The obtained noise figure is stored in the storage unit 19 of the measurement management unit 11 as a measurement result.

  In this embodiment, the noise figure at the point of the measurement frequency of 2 GHz is −140 dBm as shown in FIG. This measurement result is indicated by “x” at the point of the measurement frequency of 2 GHz in FIG.

  Next, the residual spurious determination unit 14 compares the measurement result with a threshold value (step S44).

  Specifically, the residual spurious determination unit 14 reads out -140 dBm of the measurement result from the storage unit of the measurement management unit 11, and from the table of frequency ranges and threshold values stored in the parameter management unit 14, The threshold value in the band to which the measurement frequency at the time of measurement belongs is read. Here, since the measurement frequency is 2 GHz, the residual spurious determination unit 14 reads out the threshold value −130 dBm shown in FIG.

  Next, the residual spurious determination unit 14 compares the read threshold value −130 dBm with the measurement result −150 dBm (step S44).

  In the comparison, the residual spurious determination unit 14 determines that the measurement result of −140 dBm is smaller than the threshold value of −130 dBm. This is also apparent from the fact that in FIG. 5B, the measurement result of −140 dBm is located below the threshold of −130 dBm at the measurement frequency of 2 GHz.

  Thus, when the measurement result is smaller than the threshold value, the measurement management unit 11 stores the measurement frequency at which the measurement is performed in the parameter management unit 16 (step S45). In this case, the measurement management unit 11 overwrites the list of the table of the parameter management unit 16 that has read the measurement frequency at the time of measurement. However, the measurement management unit 11 may store a measurement frequency after calibration by providing a separate table.

  Next, the measurement management unit 11 determines whether there is a next measurement frequency (step S46). Here, since 3 GHz exists as the next parameter in the measurement frequency table of the measurement management unit 11, the measurement management unit 11 continues the measurement. That is, in the flowchart of FIG. 4, the operation returns to step S42.

  Next, the measurement management unit 11 reads the next parameter of the measurement frequency shown in the list shown in FIG. 2, that is, 3 GHz, as the measurement frequency F from the table stored in the parameter management unit 16 (step S42). ).

  Next, the measurement management unit 11 measures the noise level at 3 GHz read from the measurement frequency table (step S43). At this time, the N / S controller 12 supplies the input signal including the predetermined noise signal or the input signal not including the predetermined noise signal to the measurement management unit 11 while switching the N / S 22 on / off, and performs measurement. The management unit 11 obtains measurement values in each case. Further, the measurement is performed in a predetermined resolution bandwidth stored in the parameter management unit 16.

  When the measurement is completed, the measurement management unit 11 obtains the Y factor from the measured values when N / S 22 is on and off, and obtains the noise figure of the measuring apparatus 10 at the measurement frequency of 3 GHz from a predetermined formula. The obtained noise figure is stored in the storage unit 19 of the measurement management unit 11 as a measurement result.

  In this embodiment, the noise figure at the point of the measurement frequency of 3 GHz is −155 dBm, as shown in FIG. The measurement result is a value “x” indicated by an arrow A at the point of the measurement frequency of 3 GHz in FIG.

  Next, the residual spurious determination unit 14 compares the measurement result with a threshold value (step S44).

  Specifically, the residual spurious determination unit 14 reads out −155 dBm of the measurement result from the storage unit of the measurement management unit 11, and from the table of frequency ranges and threshold values stored in the parameter management unit 14, The threshold value in the band to which the measurement frequency at the time of measurement belongs is read. Here, since the measurement frequency is 3 GHz, the threshold value of −160 dBm shown in FIG.

  Next, the residual spurious determination unit 14 compares the read threshold value −160 dBm with the measurement result −155 dBm (step S44).

  In the comparison, the residual spurious determination unit 14 determines that −155 dBm of the measurement result is larger than the threshold value −160 dBm. This is also clear from the fact that in FIG. 5B, the measurement result of −155 dBm indicated by the arrow “A” is positioned above the threshold value of −160 dBm at the measurement frequency of 3 GHz.

  As described above, when the measurement result is larger than the threshold value, the residual spurious determination unit 14 determines that there is residual spurious in the measurement frequency, and the measurement frequency shift unit 15 determines the measurement frequency in response to the resolution bandwidth. Just shift.

  However, since there is a limit on the number of times to shift, the current state is confirmed before shifting. Specifically, first, the measurement management unit 11 determines whether or not the number of times that the resolution bandwidth is added to the measurement frequency is 2 or less (step S47).

  In the present embodiment, since the measurement frequency is not yet shifted, the number of times that the resolution bandwidth is added to the measurement frequency is zero.

  If the number of times that the resolution bandwidth is added to the measurement frequency is 2 or less, that is, if the resolution bandwidth is not added to the measurement frequency, or if the number of additions is 1 or 2, the measurement management unit 11 Move to the operation.

  In the next operation, the measurement frequency shift unit 15 shifts the measurement frequency at which the current measurement is performed by one resolution bandwidth (step S48).

  Here, shifting the measurement frequency by one resolution bandwidth means adding the frequency of one resolution bandwidth to the measurement frequency, in other words, increasing the measurement frequency by a frequency corresponding to one resolution bandwidth. means.

  In this embodiment, the measurement frequency shift unit 15 shows a shift in which the resolution bandwidth is added to the measurement frequency. However, the measurement frequency shift unit 15 has a measurement point at a frequency point obtained by subtracting the resolution bandwidth from the measurement frequency. May be shifted.

  One resolution bandwidth is read from the parameter management unit 14. In the present embodiment, one resolution bandwidth is 4 MHz.

  In order to shift the measurement frequency by one resolution bandwidth, the measurement frequency shift unit 15 sets the frequency obtained by adding the frequency corresponding to the one resolution bandwidth to the measurement frequency as the measurement frequency F (step S48).

  Specifically, here, the measurement frequency shift unit 15 sets the measurement frequency F to 3 GHz of the measurement frequency plus 4 MHz of one resolution bandwidth.

  Next, the measurement management unit 11 measures the noise level at the measurement frequency F of 3 GHz + 4 MHz (step S43). At this time, the N / S controller 12 supplies the input signal including the predetermined noise signal or the input signal not including the predetermined noise signal to the measurement management unit 11 while switching the N / S 22 on / off, and performs measurement. The management unit 11 obtains measurement values in each case. Further, the measurement management unit 11 performs measurement in a predetermined resolution bandwidth stored in the parameter management unit 16.

  When the measurement is completed, the measurement management unit 11 obtains the Y factor from the measured values when N / S 22 is on and off, and obtains the noise figure of the measuring apparatus 10 at the measurement frequency 3 GHz + 4 MHz from a predetermined formula. The obtained noise figure is stored in the storage unit 19 of the measurement management unit 11 as a measurement result.

  In this embodiment, the noise figure at 3 GHz + 4 MHz of the measurement frequency F is −161 dBm as shown in FIG. In FIG. 6B, this measurement result is at the position “x” indicated by the arrow B at the point of the measurement frequency 3 GHz + 4 MHz.

  When the measurement by the measurement management unit 11 is completed, the measurement result is stored in the storage unit of the measurement management unit 11.

  Next, the residual spurious determination unit 14 compares the measurement result with a threshold value (step S44).

  Specifically, the residual spurious determination unit 14 reads out -140 dBm of the measurement result from the storage unit of the measurement management unit 11 when the measurement frequency is 3 GHz + 4 MHz, and the frequency range and threshold value stored in the parameter management unit 14 From the table, the threshold value in the band to which the measurement frequency at the current measurement time belongs is read. Here, since the measurement frequency is 3 GHz + 4 MHz, the residual spurious determination unit 14 reads out the threshold value −160 dBm shown in FIG.

  Next, the residual spurious determination unit 14 compares the read threshold value of −160 dBm with N / S 22 of the measurement result of −161 dBm (step S44).

  In the comparison, the residual spurious determination unit 14 determines that −161 dBm of the measurement result is smaller than the threshold value −160 dBm. This is apparent from the fact that in FIG. 6B, at the measurement frequency of 3 GHz + 4 MHz, the measurement result of −161 dBm indicated by “x” in the arrow B is located below the threshold value of −160 dBm.

  Thus, when the measurement result is smaller than the threshold value, the measurement management unit 11 stores the measurement frequency at which the measurement is performed in the parameter management unit 16 (step S45). In this case, the measurement management unit 11 overwrites the list of the table of the parameter management unit 16 that has read the measurement frequency at the time of measurement. However, the measurement management unit 11 may store a measurement frequency after calibration by providing a separate table.

  As a result, the measurement frequency “3 GHz” is overwritten and replaced by “3 GHz + 4 MHz”. That is, when the measurement management unit 11 executes the measurement process, the frequency of “3 GHz” is not the measurement frequency, and “3 GHz + 4 MHz” becomes the measurement point of the measurement frequency.

  Next, the measurement management unit 11 determines whether there is a next measurement frequency (step S46). Here, since 4 GHz exists as the next parameter in the measurement frequency table of the measurement management unit 11, the measurement management unit 11 continues the measurement. That is, in the flowchart of FIG. 4, the operation returns to step S42.

  Next, the measurement management unit 11 reads the next parameter of the measurement frequency shown in the list shown in FIG. 2, that is, 4 GHz, as the measurement frequency F from the table stored in the parameter management unit 16 (step S42). ).

  Next, the measurement management unit 11 measures the noise level at 4 GHz read from the measurement frequency table (step S43). At this time, the N / S controller 12 supplies the input signal including the predetermined noise signal or the input signal not including the predetermined noise signal to the measurement management unit 11 while switching the N / S 22 on / off, and performs measurement. The management unit 11 obtains measurement values in each case. Further, the measurement management unit 11 performs measurement in a predetermined resolution bandwidth stored in the parameter management unit 16.

  When the measurement is completed, the measurement management unit 11 obtains the Y factor from the measured values when N / S 22 is on and off, and obtains the noise figure of the measuring apparatus 10 at the measurement frequency of 4 GHz from a predetermined formula. The obtained noise figure is stored in the storage unit 19 of the measurement management unit 11 as a measurement result.

  In this embodiment, the noise figure at the point with the measurement frequency of 4 GHz is −160 dBm, as shown in FIG. The measurement result is indicated by “x” at the point of the measurement frequency of 4 GHz in FIG.

  Next, the residual spurious determination unit 14 compares the measurement result when the N / S 22 is on with the threshold value (step S44).

  Specifically, the residual spurious determination unit 14 reads -160 dBm of the measurement result from the storage unit of the measurement management unit 11, and from the table of frequency ranges and threshold values stored in the parameter management unit 14, The threshold value in the band to which the measurement frequency at the current measurement time belongs is read. Here, since the measurement frequency is 4 GHz, the threshold value −155 dBm shown in FIG.

  The residual spurious determination unit 14 then compares the read threshold value −155 dBm with the measurement result −160 dBm (step S44).

  In the comparison, the residual spurious determination unit 14 determines that −160 dBm of the measurement result is smaller than the threshold value −155 dBm. This is apparent from the fact that the measurement result of −160 dBm indicated by “x” is located below the threshold value of −155 dBm at the measurement frequency of 4 GHz, as shown in FIG.

  Thus, when the measurement result is smaller than the threshold value, the measurement management unit 11 stores the measurement frequency at which the measurement is performed in the parameter management unit 16 (step S45). In this case, the measurement management unit 11 overwrites the list of the table of the parameter management unit 16 that has read the measurement frequency at the time of measurement. However, the measurement management unit 11 may store a measurement frequency after calibration by providing a separate table.

  Next, the measurement management unit 11 determines whether there is a next measurement frequency (step S46). Since the next measurement frequency does not exist in the measurement frequency table of the parameter management unit 16, the calibration processing operation of the measurement management unit 11 ends.

  On the other hand, when the threshold value is equal to or lower than the measurement result (in the case of NO in step S47), the number of times the resolution bandwidth is added to the measurement frequency is 3 or more, that is, the measurement frequency is already equal to the two resolution bandwidth Although it is shifted, if the measurement result is still equal to or greater than the threshold value even at the measurement frequency point, there is a high possibility that the measurement apparatus 10 has a defect. 11 stops the measurement (step S49) and the calibration process ends.

  The above is the operation when the calibration process of the measuring apparatus 10 is executed. Thus, in the calibration process, a noise figure is obtained as a measurement result for calibration and stored in the storage unit 19, and a table of measurement frequencies with a new measurement point as a measurement frequency by shifting the measurement frequency is provided. Preparing.

  FIG. 7 is a conceptual diagram for explaining the relationship between the residual spurious and the resolution bandwidth (RBW) when the measuring apparatus 10 is calibrated. In the figure, the horizontal direction indicates the frequency in the positive direction on the right, and the vertical direction indicates dB in the positive direction on the vertical direction.

  FIG. 7A shows the case where the measurement frequency at the point of the broken line is the residual spurious 82 and the residual spurious 82 exists in the resolution bandwidth 84. In this state, the measurement result at the measurement frequency exceeds the threshold value of the display average noise level, and the measurement object 10 cannot be accurately measured by the measurement apparatus 10 at this measurement frequency.

  FIG. 7B shows a state in which the measurement frequency is a frequency that is increased by a frequency corresponding to one resolution bandwidth from the residual spurious frequency (shown by a broken line). In the resolution bandwidth 84 of the new measurement frequency, there is no residual spurious 82 of the frequency indicated by the two-dot chain line. Thus, since the point of the measurement frequency is moved by one resolution bandwidth, the measurement accuracy does not decrease.

  FIG. 8 shows an example of the configuration when measuring the noise figure of the device under test (DUT) 20 using the measuring apparatus 10 shown in FIG. In measuring the DUT 20, the measuring apparatus 10 performs the calibration process described with reference to FIG.

  When the DUT 20 is measured, the DUT 20 is connected between the nodes 20a and 20b, and the DUT 20 and the N / S 22 are connected to the measurement management unit 11 in series.

  Next, measurement for obtaining the noise figure of the device under test is performed in the order of the measurement frequencies stored in the parameter management unit 16 and overwritten in the measurement frequency table. At the time of this measurement, no residual spurious appears in the measurement frequency. Therefore, it is not necessary to consider the residual spurious when measuring by the measuring apparatus 10.

  At the time of measurement, the N / S controller 12 controls ON / OFF switching of the N / S 22 for each measurement frequency. When the N / S controller 12 turns on the N / S 22, a signal having a predetermined noise level is supplied from the N / S 22 to the DUT 20. When the N / S 22 is turned off, a signal not including the predetermined noise level is output to the DUT 20. To be supplied.

  The Y factor is obtained from the measured value by the measurement, and the total noise figure of the DUT 20 and the measuring apparatus 10 is obtained from a predetermined formula. On the other hand, the storage unit 19 of the measurement management unit 11 stores a noise figure for calibration of the measurement apparatus 10 at each measurement frequency.

  Therefore, the measurement apparatus 10 obtains the noise figure F1 of the DUT 20 from the following equation using the total noise figure F and the noise figure F2 for calibration of the measurement apparatus 10.

Total F = F1 + (F2-1) / G
Here, G is the gain of the DUT.

  As described above, when the calibration process is executed, the noise figure of the measurement apparatus 10 is obtained, and when there is residual spurious in the measurement frequency, the measurement frequency is a frequency component corresponding to the resolution. The measurement point is replaced with a new measurement frequency at the shifted point.

  For this reason, by executing the measurement process after the calibration process, the noise figure of only the DUT 20 after calibration that does not include the noise figure of the measuring apparatus 10 is obtained.

  In the above-described embodiment, when there is a residual spurious in the measurement frequency, the measurement frequency is replaced with one shifted by a frequency corresponding to the resolution of the measurement apparatus 10. However, the measurement apparatus 10 may be configured such that a new list of measurement frequencies is created without distinguishing between measurement frequencies that have been replaced or not replaced.

  As described above, according to the present embodiment, it is possible to measure the accurate noise figure of the DUT 20 without considering the influence of residual spurious due to the system design of the measuring apparatus 10. Further, according to the present embodiment, it is possible to avoid residual spurious by a simple method in which the measurement frequency point is moved by the resolution bandwidth.

10 Measuring Device 11 Measurement Management Unit 12 N / S Controller (Noise Source Controller)
14 Residual Spurious Determination Unit 15 Measurement Frequency Shift Unit 16 Parameter Management Unit 17 Input Operation Unit 18 Display Unit 19 Storage Unit 20 DUT (Measurement Object)
22 N / S (noise source)

Claims (6)

A measurement process for measuring the noise figure of the object to be measured (20) by a Y factor method using a noise source having a known excess noise ratio, and a noise source having a known excess noise ratio before the measurement process is executed. A measuring apparatus (10) for performing a calibration process using a Y factor method to obtain a calibration value,
An input operation unit (17) to which an execution instruction of any of the measurement process and the calibration process and a measurement frequency for measuring the noise figure are input;
When the calibration operation is instructed to the input operation unit, the noise figure of the measuring device is measured at the measurement frequency, and the measured noise figure of the measuring device is used as a calibration value. Performing calibration and when the input operation unit is instructed to execute the measurement process, a measurement management unit (11) for measuring the noise figure of the device under test at the measurement frequency;
A residual spurious determination unit (14) for determining whether or not the noise figure at the measurement frequency is affected by residual spurious when the measurement management unit is executing the calibration process;
When the residual spurious determination unit determines that the noise figure at the measurement frequency input by the input operation unit is affected by residual spurious, the measurement frequency is increased or decreased by a predetermined frequency. A measurement apparatus comprising: a measurement frequency shift unit (15) that shifts the measurement frequency so that the frequency becomes the measurement frequency.   The measuring apparatus according to claim 1, wherein the predetermined frequency corresponds to a resolution of the measuring apparatus.   The residual spurious determination unit compares the noise figure at the measurement frequency of the measurement device measured by the measurement management unit with a predetermined threshold value, so that the noise figure at the measurement frequency is affected by residual spurious. The measuring apparatus according to claim 1, wherein it is determined whether or not. A measurement process for measuring the noise figure of the object to be measured (20) by a Y factor method using a noise source having a known excess noise ratio, and a noise source having a known excess noise ratio before the measurement process is executed. A measurement method using a measurement apparatus (10) for performing a calibration process for obtaining a calibration value by using a Y-factor method,
An input step in which an execution instruction for any of the measurement process and the calibration process and a measurement frequency for measuring the noise figure are input;
When execution of the calibration process is instructed in the input step, the noise figure of the measurement apparatus is measured at the measurement frequency, and the measurement apparatus is calibrated using the measured noise figure of the measurement apparatus as a calibration value. When the execution of the measurement process is instructed in the input step, a measurement step of measuring the noise figure of the device under test at the measurement frequency;
A residual spurious determination step for determining whether or not the noise figure at the measurement frequency is affected by residual spurious when the calibration process is being performed in the measurement step;
In the residual spurious determination step, a frequency obtained by increasing or decreasing the measurement frequency by a predetermined frequency when it is determined that the noise figure at the measurement frequency input in the input step is affected by the residual spurious. And a measurement frequency shift step for shifting the measurement frequency so that becomes the measurement frequency.   The measurement method using the measurement apparatus according to claim 4, wherein the predetermined frequency corresponds to a resolution of the measurement apparatus.   In the residual spurious determination step, by comparing the noise figure at the measurement frequency of the measuring device measured in the measurement step with a predetermined threshold value, whether or not the noise figure at the measurement frequency is affected by residual spurious. The measurement method using the measurement apparatus according to claim 4 or 5, wherein the determination is performed.

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